JPH02222181A - Rare earth element added light-coupled waveguide - Google Patents

Abstract

PURPOSE:To realize laser oscillation and amplification action having excellent efficiency by adding a rare earth element to a core wavegudie and a clad. CONSTITUTION:A buffer layer 2 having a refractive index of nb is formed onto a substrate 1 composed of a semiconductor, glass, a ferrodielectric, a magnetic substance, etc., core waveguides 3-1 and 3-2 having a refractive index of nc (nc>nb) and an approximately rectangular cross section are shaped onto the layer 2, and the whole upper section of the core waveguides is covered with a clad 4 having a refractive index of ncl (ncl<nc). A rare earth element is added to the core waveguides 3-1, 3-2 and the clad 4. The waveguides 3-1 and 3-2 have adjacently arranged coupling sections 5, and an optical signal 6 mutually interferes and is propagated while shifting between the waveguides 3-1, 3-2, is transferred from one to the other in the wvaveguides in response to coupling length (l), and it divided into both waveguides.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical coupling waveguide doped with rare earth elements.

[Prior art] In recent years, research on optical fiber lasers in which rare earth elements are added to the core of the optical fiber has become active, and optical fiber lasers for various laser light sources,
It has started to attract attention as an optical amplification medium.

Figure 6 shows an example of the configuration of a conventional optical fiber laser.
-16, PP, 31-37. January 1988). This is an optical resonator constructed by having both end faces of an optical fiber doped with a rare earth element added to the core of the optical fiber directly contact a laser mirror, or by depositing a dielectric multilayer film on both end faces of the optical fiber. . The excitation light source is an Ar ion laser (wavelength 514.5n) and a dye laser (wavelength 650nm).
, end face excitation is performed using a semiconductor laser (wavelength: 830 nm). Further, as an example of an optical amplifier, the configuration shown in FIG. 7 has been proposed by the above-mentioned authors. That is, the signal light is propagated in an optical fiber doped with rare earth elements, the excitation light is combined using an optical fiber coupler, and is separated using an optical fiber coupler.47. It is made up of j.

[Problem to be solved by the invention] The above-mentioned optical fiber laser and optical fiber amplifier have the following characteristics: ■ Because the core diameter of the optical fiber is small, the pumping power density becomes large and the pumping efficiency can be increased.■ Interaction Characteristics include being able to have a long length ■ Low loss, especially in the case of silica fiber ■ Flexibility. However, when trying to realize a so-called multifunctional optical integrated circuit by combining other optical components such as a light source, optical receiver, optical modulator, optical coupler, optical multiplexer/demultiplexer, optical filter, and optical switch, the implementation becomes difficult. There were problems in that it was complicated, it was difficult to reduce costs, and it was not easy to make it smaller and improve its performance.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above, and to provide an optical coupling waveguide that can be easily realized as a multifunctional optical integrated circuit.

[Means for Solving the Problem] That is, the present invention provides at least two core waveguides (refractive index n c1) via a cladding with a low refractive index (refractive index n c1).
By using an optical coupling waveguide in which the core and cladding are doped with rare class 2 elements, the above "1" can be achieved.
It was designed to achieve the target.

``Operation''] In the optically coupled waveguide, optical signals propagate between the two core waveguides without changing or interfering with each other, and at a certain coupling length, the optical signal propagates completely from one core waveguide to the other core waveguide. When the coupling length is different, the optical signals propagate in sync with each other. Therefore, if rare earth elements are doped not only in the core waveguide but also in the cladding, the cladding between the core waveguides can also greatly contribute to the laser function and amplification function, resulting in more efficient lasers and amplifiers. It is possible to realize this. Furthermore, by forming a mirror, a reflective film, etc. on the optical coupling waveguide, and mounting an active optical element such as a semiconductor laser or a light receiving element, it is possible to realize a multifunctional optical integrated circuit.

[Example] FIG. 1 shows an embodiment of the optical coupling waveguide of the present invention.

3(a) is a plan view, and FIG. 2(b) is a side view thereof. A buffer layer 2 with a refractive index of nb is provided on a substrate 1 made of semiconductor, glass, ferroelectric material, or magnetic material, and a core conductor having a substantially rectangular cross section with a refractive index of nb (nc>nb) is provided thereon. It has a structure in which wave paths 3-1 and 3-2 are formed, and the entire top thereof is covered with a cladding 4 having a refractive index of ncl (ncl<nc). Rare earth elements are core waveguide 3-
1.3-2 and cladding 4. The two core waveguides 3-1 and 3-2 have coupling portions 5 arranged close to each other, and the coupling length Ω is defined as the complete coupling length L (the optical signal 6 incident on the core waveguide 3-1). is the core waveguide 3-2
n Ω − (n=1. 3. 5...) ... (1
), it operates as a 3d13 coupler. Moreover, the wavelength λ1. which is incident on the core waveguide 3-1. In order to demultiplex the optical signal of λ2 to 7-1, the wavelength λ1 to 7-2, and the wavelength λ2 to 7-2, the complete coupling lengths for the wavelengths λ1 and λ2 are respectively L(λ1) and L(λ2), as follows. All you have to do is choose.

Here, unless a rare earth element is added to the cladding 4, the laser oscillation or amplification effect of the optical signal propagating within the cladding 4 of the coupling portion 5 will not be promoted. On the other hand, if a rare earth element is added to the cladding 4, the two effects are promoted and extremely efficient laser oscillation or amplification effect can be realized. Sunaichi,
This has the effect of equivalently increasing the active waveguide length.

2 to 6 show cross-sectional views of coupling portions of various optical coupling waveguides of the present invention.

FIG. 2 shows a case where three core waveguides 3-1, 3-2, and 33 are arranged in parallel. For example, it can be used to branch or demultiplex an optical signal incident on the core waveguide 3-1 to the core waveguide 3-23-3.

FIG. 3 also shows an embodiment in which three core waveguides 3-1.3-4.35 are arranged in parallel. This can be used to configure optical splitters, optical multiplexers/demultiplexers, optical resonators, etc. by varying the structural dimensions and refractive index of 3-4, 3-5 for the 3 core waveguides. This is a suitable configuration.

Similarly, in FIG. 4, optical filters, optical resonators, and optical multiplexers and demultiplexers can be created by making the structural dimensions and refractive index of the core waveguide 3-4 different from the core waveguide 3-1. It is possible to realize this.

FIG. 5 shows an example of a ridge-type optical coupling waveguide, which is different from the buried optical coupling waveguide described so far. That is, the cladding 8 is composed of a thinner film than the conventional cladding 4.

FIG. 6 shows an embodiment in which the buffer layer 2 is not provided. In this case, the substrate 1 serves as a buffer layer 2, the refractive index of which is chosen to be ns.

2. In the embodiments shown in FIGS. 1 to 6, for example, Si or 5102 is used for the substrate 1, and Si02P is used for the buffer layer 2 so that the refractive index is equal to 5iOz.
20!1-B20] type glass is used. The core waveguide 3 is made of 5i02T i02 glass, Er, N
A material to which at least one rare earth element such as d, Ce, etc. is added is used. 5i02-P, 20582 for cladding
03 series glass to which rare earth elements such as Er, Nd, and Ce are added is used. In addition, the waveguide dimensions are:
The signal light propagated within the core and the oscillation signal light when laser oscillated are selected to be transmitted in single to mote mode. for example,
When the signal light and laser oscillation signal light are in the 1.5 μm band, the person in the leading wave path.

Considering the compatibility with the single mote optical fiber connected to the output end, the width and thickness of the core waveguide is approximately 10 μm.1 The refractive index difference between the core waveguide and the cladding is approximately 0.4%, and the thickness of the buffer layer is The thickness of one cladding of approximately 10 μm is approximately 30 μm.

FIG. 7 shows an embodiment of the ring-shaped resonator of the present invention. In this embodiment, for the excitation light source (wavelength λp) that entered the core waveguide 9-1 from the direction of the arrow 12-1,
By providing a mirror 13 with a reflectance of 9926 on the input side and a mirror 14 with a reflectance of 98% on the output side,
Continuous wave light is generated over wavelengths λ01 to λOn. Here, the ring-shaped waveguide 10 is coupled to core waveguides 91 and 9-2 through coupling portions 11-1 and 11-2. Then, this ring-shaped waveguide causes coupling to an optical signal of a desired wavelength (for example, λ(13)) from the wavelengths λ0 to λn, and connects the optical signal with the arrow 12-
3, it is designed to receive optical signals. In addition, as another method of using this embodiment, by propagating within the core waveguide 9-1 for the signal light with wavelengths λsl to λsn and the pumping light with wavelength λp incident from the direction of arrow 12-1, ``2 amplifying the signal light, coupling a certain wavelength (for example, λs2) of the signal light to the ring-shaped waveguide 10, and taking out the signal light with the wavelength λS2 in the direction of arrow 12-3, It is also possible to use it as a so-called optical demultiplexer.

FIG. 8 shows an embodiment of a multifunctional optical integrated circuit using the optical coupling waveguide of the present invention. Here, an example is shown in which the wavelength of the semiconductor laser 15 used as the excitation light source is stabilized. ing. . That is, when the optical signal of the semiconductor laser 15 is made to enter the core waveguide 9-1 through the mirror 13 and the optical signal of the oscillated wavelength is emitted in the direction of the arrow 122 through the mirror 14, a part of the optical signal of the semiconductor laser 15 is is guided into the core waveguide 9-2 through the ring-shaped waveguide 10 and propagated in the direction of the arrow 12-3 to the light receiving element 16.
The light is received by the electric drive circuit 1 through the electric reception circuit 18.
7 to stabilize the wavelength of the semiconductor laser 15. And as a result, arrow 12-
It becomes possible to stabilize the wavelength of the oscillated light emitted in two directions.

Note that the present invention is not limited to the above embodiments. First, the glass composition of the core waveguide and cladding is 5IO2, B, P, and Ti.
, Ge, F, etc., and a rare earth element added to it, or SiO2 with an alkali metal, alkaline earth metal, etc. additive, B, P, or Ti.
It is also possible to use a material containing at least one additive such as , Ge, or F to which a rare earth element is added. In addition, 5i02 or B is added to 5i02 in the buffer layer.

A material containing at least one of additives such as P, Ti, Ge, F, alkali metals, and alkaline earth metals can be used.

[Effects of the Invention] As described above, the present invention improves the laser oscillation of the optical signal propagating in the cladding at the coupling part by adding a rare earth element to the core waveguide and the cladding of the optical coupling waveguide having a planar structure. Alternatively, the amplification effect can be promoted, and extremely efficient laser oscillation or amplification effect can be realized. Furthermore, since optical active elements and mirror reflective films can be easily mounted, it becomes possible to realize compact and multifunctional optical integrated circuits.

[Brief explanation of the drawing]

1 and 7 show examples of the optical coupling waveguide of the present invention, and FIGS. 2 to 6 show cross-sectional views of various embodiments of the optical coupling waveguide of the present invention. It is something. FIG. 8 shows an embodiment of a multifunctional optical integrated circuit using the optical coupling waveguide of the present invention. FIG. 9 shows an example of the configuration of a conventional optical fiber laser, and FIG. 10 shows an example of the configuration of a conventional optical fiber amplifier. 1. Substrate, 2. Buffer layer, 3-1.3-2.3-3. 3-4°9-1. ! J-2: core waveguide, 8. cladding, : coupling part, 0: ring-shaped waveguide, 3.14: mirror 5: semiconductor laser, 6: light receiving element. Closed (b) 7C Panfei Day 1 Figure 1 Denryo - F, 7 Do 4th Interchange

Claims (1)

[Claims] 1. At least two core waveguides (refractive index nc, nc>nc1) via a cladding with a low refractive index (refractive index nc1)
1. An optical coupling waveguide in which the core waveguide and the cladding are doped with a rare earth element. 2. An optical coupling waveguide according to item 1, characterized in that a buried type or a ridge type is used as the waveguide structure. 3. An optical coupling waveguide according to item 1, characterized in that a directional coupler or a ring resonator is used as the optical coupling waveguide. 4. In the optical coupling waveguide described in items 1 to 3, an optical coupling in which a mirror, a reflective film, an active optical element such as a semiconductor laser, a light receiving element, or an electronic circuit is mounted at the input/output end or in the middle of the waveguide. waveguide.